This invention relates to a device to hold a vehicle to a loading dock. In particular, it relates to a device that prevents vehicle movement away from a loading dock as loading and/or unloading operations of the vehicle occur.
The traditional manner of restraining a vehicle so that it does not move during loading operations is to use wheel chocks. While inexpensive and generally efficient, they are dependent on the operator and must be properly placed to eliminate vehicle creep. The tendency to move in small increments that over a protracted loading operation may result in a significant distance between the back of the truck and the dock face. Additionally, in some conditions, such as ice and snow, they may slide.
Given these problems with wheel chocks, a variety of devices have been proposed and placed into commercial use that affirmatively grab onto a portion of the truck. The most popular part to grab is the vehicle ICC bar, which by regulation must be placed in a specific location range under the rear of the vehicle. While offering some improvements over vehicle chocks, these devices are more expensive and introduce a new set of engineering problems. First is that as the vehicle is unloaded it tends to float, that is upward movement of the truck bed. The vehicle restraint must be able to accommodate such movement. The converse case of vehicle loading also presents a problem since the device must have sufficient range so as not to lock up under such downward force. Movement toward and away form the dock must also be accommodated. The ICC bar may be placed within a range from the rear of the truck and any device requires operating space. Thus, a so-called capture range exists where the device will engage the ICC bar. The device must however function in such a manner to grab the bar yet not have excessive play that allows the truck to move away from the dock.
U.S. Pat. No. 4,146,888 deals with an attempt to utilize an hydraulic device secured to the dock floor having a securing element coupled to the truck bed. The device requires a self-alignment of the hydraulic cylinder to be mounted on the dock unit and also uses an attaching hook carried by the piston exposed portion and having an end adapted to be releasably connected to the truck. Similarly. U.S. Pat. No. 4,191,503, which is an extension on the technique. requires a locking assembly which is elongated having a frictional member and manually actuated means, that is the handle for moving the frictional member. Neither of these devices grab onto the ICC bar. They tend to interfere with loading operations and may not work on a wide variety of trucks.
U S. Pat. No. 4,208,161 illustrates a device to lock on to a vehicle ICC bar. The device is mounted to the dock face and employs a hook element hingedly moved into an upward engagement position. The device is operated at dock level and cannot accommodate vehicle float during loading and unloading operations.
The next generation of vehicle restraints that grabbed the ICC bar are represented by patents that use the concept of utilizing a carriage which is mounted on the dock face for vertical movement which carried a rotating hook. Thus, U.S. Pat. No. 4,264,259 defines such a carriage having first and second sections and the hook again defined as having a distal portion to interlockingly engage a portion of the parked vehicle. The vertically movable carriage compensates for float and accommodates vehicle ICC bars of different sections U.S. Pat. No. 4,379,354 represents another example of a carriage type device. U.S. Pat. No. 4,267,784 is a variation of the device of the 161 patent but defines a specific locking arrangement and actuating member. Thus, the device employs a plurality of selective operative positions with the lock component having a plurality of annularly spaced pockets.
Further patents using the vertically movable carriage principle are U.S. Pat. No. 4,282,261 which defines a commercial device marketed by Rite-Hite Corporation under the name "ADL". This device has the motor for actuating the engaging hook carried on the vertically moving carriage. A problem with this type of device is that the rearward movement of the truck is employed to drive the carriage down as the ICC bar slides along a ramp surface. If the truck backs down too fast the carriage may be bent jamming the hook. Also, the ICC bar itself may be bent due to contact with the carriage. U.S. Pat. Nos. 4,373,847 and 4,443,150 deal with the manual vehicle locking configurations. These devices offer simplicity but sacrifice device range. U.S. Pat. Nos. 4,472,009 and 4,560,315 are variations of the carriage carrying a rotating hook.
U.S. Pat. No. 4,630,989 represents a different design system to the vehicle restrain problem. That system employs a pivotal bar mounted on vertically extending frame members so that it extends into a vertical position from a generally horizontal position. The bar is actuated by means of an hydraulic cylinder which is secured to mounting bracket 30. When hydraulic pressure is released, the return springs cause retraction of the bar.
In the device of the '989 patent, the hydraulic cylinder is secured adjacent the forward end of the horizontal bearing face 14 and pivotally secured to the pivotal locking bar so that it is angled rearwardly toward the vertical securing face.
U S. Pat. Nos. 4,888,325 and 4,647,951 deal generally with different types of structures having rather complicated linkages to effectuate locking and unlocking. In the case of the '325 patent, a slide mechanism is used which employs a rack and pinion for purposes of effectuating a linear upward movement of the slide. In the '941 patent, defines a parallelogram type linkage which pivotally interconnects the frame for purposes of moving the engaging member into and out of its operative position. These devices, while offering extended range, do so using complicated linkages that are not suited for the dirty, open environment of a loading dock.
U.S. Pat. No. 4,695,216 describes a device having a slide for the ICC bar, the slide having a recess disposed inwardly in a direction toward the supporting structure. When the ICC bar interacts on the slide, it engages an inclined surface to wedge the slide downwardly against the force of a biasing means to effect engagement with the ICC bar and with the recess.
A different design approach is found in U.S. Pat. Nos. 4,400,127 and 4,555,211 relate to the commercial line of restraints made by Serco under the name AVR 100-300. Those devices use a pair of independently rotated arms, each carrying a series of staggered teeth, the arms spring, pneumatically or hydraulically actuated. Since the teeth will engage at a different location with respect to the dock face the truck will be held in position at a distance closest to the dock. The pneumatic operation accommodates float. These devices while offering advantages still are mounted on the dock approach and have limitations in range.